Brain Waves And Rem Sleep: What's The Link?

The physiological indicators that suggest a person is in REM sleep include rapid eye movement, irregular breathing, elevated heart rate, and increased brain activity. During REM sleep, the eyes move rapidly behind closed eyelids, the heart rate speeds up, and breathing becomes irregular. Brain activity during REM sleep is also highly active, with brain waves resembling the pattern seen during wakefulness.

Brain activity

During REM sleep, the brain uses as much energy as it does when awake, or even more. The rate of energy use in non-REM sleep is 11-40% lower. The brain waves during non-REM sleep are slow delta waves, which differ from the brain waves of REM sleep.

The brain's frontal and posterior areas are less coherent in most frequencies during REM sleep, which has been linked to the chaotic experience of dreaming. However, the right and left hemispheres of the brain are more coherent with each other during REM sleep, especially during lucid dreams.

The brain's superior frontal gyrus, medial frontal areas, intraparietal sulcus, and superior parietal cortex show equal activity in REM sleep as in wakefulness. These areas are involved in sophisticated mental activity.

The amygdala is also active during REM sleep and may participate in generating electrical bursts called "ponto-geniculo-occipital waves" (PGO waves). Experimental suppression of the amygdala results in less REM sleep.

The transition to REM sleep brings marked physical changes, beginning with PGO waves originating in the brain stem. REM sleep is punctuated and immediately preceded by these waves, which occur in clusters about every 6 seconds for 1-2 minutes during the transition from deep to paradoxical sleep.

The electrical and chemical activity regulating REM sleep seems to originate in the brain stem, with the neurotransmitter acetylcholine being abundant and monoamine neurotransmitters histamine, serotonin, and norepinephrine being almost completely absent.

REM sleep is also called paradoxical sleep because of its similarities to wakefulness. The brain acts as if it is awake, but the body is paralysed, with a loss of muscle tone.

Eye movement

REM sleep is the fourth of four stages of sleep. During this stage, the eyes move rapidly behind closed eyelids, and the brain activity is similar to its activity when a person is awake. The brain waves are fast, low-amplitude, and desynchronized, resembling the pattern seen during wakefulness.

The transition to REM sleep brings about marked physical changes, beginning with electrical bursts called ponto-geniculo-occipital waves (PGO waves) originating in the brain stem. The body abruptly loses muscle tone, a state known as REM atonia. This almost complete paralysis of the body is achieved through the inhibition of motor neurons.

REM sleep is physiologically different from the other phases of sleep, which are collectively referred to as non-REM sleep (NREM sleep or NREMS). The absence of visual and auditory stimulation (sensory deprivation) during REM sleep can cause hallucinations.

During a typical night of sleep, humans experience about four or five periods of REM sleep. The first REM episode occurs about 70 minutes after falling asleep, and each cycle, including a larger proportion of REM sleep, lasts about 90 minutes. The first REM cycle is typically the shortest, around 10 minutes, with each subsequent cycle getting longer, up to an hour.

REM sleep typically occupies 20-25% of total sleep in adult humans, and as people age, they tend to sleep less overall but spend about the same amount of time in REM sleep.

Muscle tone

During REM sleep, the body experiences muscle atonia, or muscle paralysis, which is a reduction in muscle tone. This is a normal function of REM sleep, and it is thought to be a protective measure to stop people from acting out their dreams and injuring themselves.

During REM sleep, the brain is highly active, but the body's muscles are temporarily paralysed. This paralysis is caused by descending SLD glutamatergic projections that activate the ventromedial medulla, and spinal cord interneurons. This results in muscle atonia and the suppression of phasic muscle twitches in the spinal musculature.

However, people with REM sleep behaviour disorder (RBD) maintain muscle tone during REM sleep, allowing them to move and act out their dreams. This can result in minor movements, such as leg twitches, or more complex behaviour that may cause serious injury. RBD is often associated with certain neurological disorders and can be a symptom of adverse reactions to certain drugs or drug withdrawal.

Heart rate

The sleep cycle consists of three stages of non-REM sleep and one stage of REM sleep. After falling asleep, a person first enters non-REM sleep, which is further divided into four stages. The first stage is transitional, lasting 5-10 minutes, and the person can be easily woken up. In the second stage, the person enters light sleep, lasting 10-25 minutes, and their heart rate and breathing slow down further as their body temperature drops. The third and fourth stages constitute deep sleep, which is harder to be roused from. In adults, the third stage makes up about 25% of total sleep time.

After non-REM sleep, the person enters the REM stage, which is characterised by rapid eye movement, increased brain activity, and irregular breathing. The heart rate increases and can be monitored to determine the stage of sleep. The cycle then repeats, with each cycle lasting between 90 and 120 minutes.

The heart rate is an important indicator of the sleep stage and can be used to differentiate between light and deep sleep. It also helps detect restlessness and short periods of wakefulness during sleep. By tracking heart rate variability, devices like Fitbit can estimate sleep cycles and provide insights into sleep quality.

Breathing

During REM sleep, a person's breathing becomes irregular and their heart rate rises. The first REM cycle of a sleep period is typically the shortest, lasting around 10 minutes. Each cycle that follows is longer than the last, with the final one lasting up to an hour.

The transition to REM sleep brings about marked physical changes, including electrical bursts called "ponto-geniculo-occipital waves" (PGO waves) originating in the brain stem. The body abruptly loses muscle tone, a state known as REM atonia.

During REM sleep, the body suspends homeostasis, allowing large fluctuations in respiration, thermoregulation, and circulation, which do not occur during any other sleep or waking state. Generally, respiratory reflexes such as the response to hypoxia diminish, and the brain exerts less control over breathing.

Ventilation data during REM sleep suggests that hypoventilation occurs in a similar way to during non-REM sleep. Several factors contribute to hypoventilation during non-REM sleep, and possibly REM sleep, such as reduced pharyngeal muscle tone. During REM sleep, there is also reduced rib cage movement and increased upper airway resistance due to the loss of tone in the intercostals and upper airway muscles.

In summary, breathing patterns can be a strong indicator of the stage of sleep a person is in. During non-REM sleep, breathing slows down, while during REM sleep, it becomes irregular and is characterised by erratic respiratory flow.

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